#include "types.h"
#include "stat.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "traps.h"
#include "syscall.h"
#include "spinlock.h"
#include "buf.h"
#include "fs.h"
#include "fsvar.h"
#include "elf.h"
#include "file.h"
#include "fcntl.h"

// User code makes a system call with INT T_SYSCALL.
// System call number in %eax.
// Arguments on the stack, from the user call to the C
// library system call function. The saved user %esp points
// to a saved program counter, and then the first argument.

// Fetch the int at addr from process p.
int
fetchint(struct proc *p, uint addr, int *ip)
{
    if(addr >= p->sz || addr+4 > p->sz)
        return -1;
    *ip = *(int*)(p->mem + addr);
    return 0;
}

// Fetch the nul-terminated string at addr from process p.
// Doesn't actually copy the string - just sets *pp to point at it.
// Returns length of string, not including nul.
int
fetchstr(struct proc *p, uint addr, char **pp)
{
    char *cp, *ep;

    if(addr >= p->sz)
        return -1;
    *pp = p->mem + addr;
    ep = p->mem + p->sz;
    for(cp = *pp; cp < ep; cp++)
        if(*cp == 0)
            return cp - *pp;
    return -1;
}

// Fetch the argno'th word-sized system call argument as an integer.
int
argint(int argno, int *ip)
{
    struct proc *p = curproc[cpu()];

    return fetchint(p, p->tf->esp + 4 + 4*argno, ip);
}

// Fetch the nth word-sized system call argument as a pointer
// to a block of memory of size n bytes.  Check that the pointer
// lies within the process address space.
int
argptr(int argno, char **pp, int size)
{
    int i;
    struct proc *p = curproc[cpu()];

    if(argint(argno, &i) < 0)
        return -1;
    if((uint)i >= p->sz || (uint)i+size >= p->sz)
        return -1;
    *pp = p->mem + i;
    return 0;
}

// Fetch the nth word-sized system call argument as a string pointer.
// Check that the pointer is valid and the string is nul-terminated.
// (There is no shared writable memory, so the string can't change
// between this check and being used by the kernel.)
int
argstr(int argno, char **pp)
{
    int addr;
    if(argint(argno, &addr) < 0)
        return -1;
    return fetchstr(curproc[cpu()], addr, pp);
}

extern int sys_chdir(void);
extern int sys_close(void);
extern int sys_dup(void);
extern int sys_exec(void);
extern int sys_exit(void);
extern int sys_fork(void);
extern int sys_fstat(void);
extern int sys_getpid(void);
extern int sys_kill(void);
extern int sys_link(void);
extern int sys_mkdir(void);
extern int sys_mknod(void);
extern int sys_open(void);
extern int sys_pipe(void);
extern int sys_read(void);
extern int sys_sbrk(void);
extern int sys_unlink(void);
extern int sys_wait(void);
extern int sys_write(void);
extern int sys_myread(void);
extern int sys_mywrite(void);

void
syscall(void)
{
    struct proc *cp = curproc[cpu()];
    int num = cp->tf->eax;
    int ret = -1;

    switch(num){
        case SYS_fork:
            ret = sys_fork();
            break;
        case SYS_exit:
            ret = sys_exit();
            break;
        case SYS_wait:
            ret = sys_wait();
            break;
        case SYS_pipe:
            ret = sys_pipe();
            break;
        case SYS_write:
            ret = sys_write();
            break;
        case SYS_read:
            ret = sys_read();
            break;
        case SYS_close:
            ret = sys_close();
            break;
        case SYS_kill:
            ret = sys_kill();
            break;
        case SYS_exec:
            ret = sys_exec();
            break;
        case SYS_open:
            ret = sys_open();
            break;
        case SYS_mknod:
            ret = sys_mknod();
            break;
        case SYS_unlink:
            ret = sys_unlink();
            break;
        case SYS_fstat:
            ret = sys_fstat();
            break;
        case SYS_link:
            ret = sys_link();
            break;
        case SYS_mkdir:
            ret = sys_mkdir();
            break;
        case SYS_chdir:
            ret = sys_chdir();
            break;
        case SYS_dup:
            ret = sys_dup();
            break;
        case SYS_getpid:
            ret = sys_getpid();
            break;
        case SYS_sbrk:
            ret = sys_sbrk();
            break;
        case SYS_myread:
            ret = sys_myread();
            break;
        case SYS_mywrite:
            ret = sys_mywrite();
            break;
        default:
            cprintf("unknown sys call %d\n", num);
            // Maybe kill the process?
            break;
    }
    cp->tf->eax = ret;
}